Triethylamine-based catalysts for the melt polymerization of carbonate monomers

Abstract

This study determined that both triethylamine hydrochloride (TEA·HCl) and TEA can catalyze the melt polymerization of several carbonate monomers at 65–150 °C. TEA·HCl's catalytic activity is especially noteworthy because it is a common by-product in the synthesis of carbonate monomers. Melt polymerizations of trimethylene carbonate (TMC) catalyzed with TEA achieved monomer conversions ranging from 97% in 6 h at 85 °C to 98% in 1 h at 110 °C and those catalyzed with TEA·HCl ranged from 98% in 12 h at 85 °C to 98% in 1 h at 110 °C using a monomer : initiator : catalyst ratio of 50 : 1 : 0.1. By contrast, TMC polymerizations conducted with stannous octoate, a widely used catalyst, required at least twice as long to achieve the same monomer conversion (24 h at 85 °C and 2.5 h at 110 °C). Catalyst-free polymerization was also observed at temperatures and timespans below those previously reported, with 99% conversion in 32 h at 85 °C and 99% conversion in 2.5 h at 110 °C.